We now have a few small crystals of CDR (calmodulin) that diffract to nominal 4 A resolution. We are focussing nearly all of our resources on two goals: We will record a 5.5 A sphere of data from these crystals of the native CDR, using a diffractometer in the U.Va. Chemistry Department. Kretsinger and Barry (1975, ref #26) predicted a structure for molecules comprised of four EF-hand domains. We will use Patterson superposition methods (rotation function) to confirm or refute this model and, if correct, to determine the orientation of the molecule within the crystallographic unit cell. Our second goal is to grow larger CDR crystals in quantity. From these crystals we will collect high resolution diffraction data by the precession method. For the high resolution crystal structure determination and refinement we may need from only the native protein, having derived the initial phase informaton from our predicted model. If one heavy atom derivative is required, we will focus on the replacement of calcium by one of the lanthanides.